Characterization and Evaluation of Commercial Tracers for X-Space Magnetic Particle Imaging

Commercial magnetic particle imaging (MPI) tracers are utilized for many applications including as reference materials for comparing tracer performance, but comparative measurements of many tracers on a single imaging platform are uncommon. This study uses relaxometry and 2D imaging in a pre-clinical MOMENTUM scanner to characterize and evaluate the performance of six common commercial tracers for MPI: Synomag-D Plain, Synomag-D NH2, Synomag-D PEG, Perimag, Vivotrax, and Vivotrax Plus. Repeated measurements of samples showed considerable variability while inter-sample differences were generally negligible. Sensitivity between the two modes is strongly correlated while resolution of the two modes was only moderately correlated. Further, relaxometric measurements tend to predict better resolution than is achieved in 2D imaging. All evaluated tracers have resolutions within 1 mm of each other on the MOMENTUM imager. These results illustrate that relaxometer measurements can be used to broadly predict MPI performance but do not accurately recreate the physical processes or differences in hardware and software of MPI. This study provides MPI measurements of tracers that may be useful to researchers while highlighting the challenges of making comparisons between tracers due to variation within samples and across different measurement techniques and instruments.